The present invention relates to a rotary or slide potentiometer (acting as a selector switch), and a method for producing the same.
For the purpose of controlling or regulating the speed of electric machines, or of temperatures, for example of heating appliances, ironing appliances, or the like, it has been known before to provide, in addition to the respective electronic or electric circuit which may consist of a conventional phase control or the like, regulating means or actuating elements which can be actuated by the operator to pre-set a specific speed or a pre-determined temperature.
While these regulating means consist usually of potentiometers in the form of rotary or slide potentiometers, one very often provides additional locking means which are felt by the operator when he adjusts or turns the actuating means so that they will effect the desired regulating steps. This type of regulation is not only sufficiently exact for most applications, but in addition preferred because it provides the user with clear information on the current operating condition--in the case of an iron, for example, a first or lower temperature range for sensitive fabrics, a mean temperature range and a full-load range. When the existing potentiometer is, thus, anyway employed in steps only so that its transition areas are substantially superfluous, the use of such potentiometers will provide the considerable additional disadvantage that their inaccuracies are as high as .+-.20% so that under certain circumstances one would even have to consider an additional need for calibration.
If one chooses to select switches for this purpose--a solution which would seem imaginable--the disadvantage of the considerably higher switch requirements of a selector switch would even be aggravated by the fact that the conducting paths of the circuit board would have to be upgraded at substantial cost, at least in the switch area, i.e. the copper layers would have to be silver-plated, if they are swept by a switching contact. Further, one would in this case have to put up with the additional disadvantage that certain circuit elements have to be accommodated on the printed circuit side of the board because not all components can be accommodated on the component side--a fact which may give rise to assembly and space problems. Finally, upgrading of the conductive paths would again lead only to flat contact points while for efficient contact-making the surfaces getting into contact with each other should, ideally, have a shape as close as possible to spherical. And the use of punched parts in the construction of the switch would also require the said parts, which are usually made from copper, to be coated with carbon or gold or silver, and render their assembly correspondingly troublesome.
Now, it is the object of the present invention to provide a rotary or slide potentiometer acting as a selector switch, which can be used without any problems for the purposes described above, which does not give any problems as regards assembly and application, and which on the other hand offers considerably higher precision than, for example, noncalibrated potentiometers with mechanical stop means.